Frequency conversion apparatus



2 sheets-sheet 2 W. W. HANSEN ET AL` FREQUENCY CONVERSION APPARATUS 2 5 aa I Tl /l /40/32 a7 sa I'l' 49 a9 oct. 26, 1948-.

Filed July l2, 1943 Patented Oct. 26, 1948 Y., lFREQUENCY CONVERSION:APPARA'IUSl1 William W. Hansen and."R u ssel l`, L" Varianfarden City,`N. Y., assignors to The Sperry Corporatiom a corporation of Delaware Application JulylZ, 1943T SeriaLNo. 494,284

"j The present invention relates to electronics and is; especially concerned with frequency conversion methods 'andf'apparatus.v y

1""V'Vh'ile various frequency multiplication arrangements have beens'uggested and employed for some "electronfdis'charge'apparatus, no reliable'frequency'division devices areavailable for 'microwave apparatus tlo"ourfknowledge. In` the ultra high frequency eld, whereinfrequencies yiri'the order of 3X l0B t-o'IBXlOQ'cycles per second and higher v are presentwthereis a growingv need for vsuch frequencydivision devices, and the presentinvention solves'many ofthe attendant problems# As' will appear, tliej'invention is yespecially advantageous Where stabilization `of ultra vhigh frequencyoutput is dificult, and its principles are also yapplicable for frequency multiplication.

25|c1aims. (forato-eww Litis amajor object of our invention to" provide novel ultraA highfrequency division and multiplication'methoclsand apparatus.H

further'object ofthe invention is to provide frequency Conifer-sionA apparatus embodying novel frequency mixingand feed-baul; arrangements. "It isa further object of the invention to provide novell frequency division apparatus embodying frequency' multiplier and associated mixing arrangements-; j .o f l i i riurther object; ofthe inventionjis to provide embodying frequency division and multiplication melthvldsjaeiiapparatus., 'In 'an impftant Phase, this object is'especiallyapplicable to automatic frequency control of ultrafhigh frequencycavity resonator devices.

A further object of theinvention is to provide novel ultra high` frequency conversion apparatus ofthe avityrsonatortyp I A furthe-object of the invention is to provide novel ultra-high frequency cavity resonator structure.` Y Further vobjects of theinvention Will appear presently as the descriptionv proceeds lin 'connection vvith the appended drawingswherein: vFig.' "1f is a diagrammatic vievv illustrating Acertair"`basi'c principles`"'of the invention; Mlig; 2 is' a'diagrammaticview illustrating practi-calapplication of theprinciples of Fig. 1 toV an automatic frequency control js5 f stem;` j Q 'I VFig'.1 '3 'is ajdiagrammatic'viewillustrating basic principles-cfa further embodiment of the invenltion employinga multiplier`system; "Fig: eis a" diagrammatic View iilustraiing pracclaims and the annexed Eig. '5 is-adlagr I 'nmaticview illustrating prinipl'es of the invention` ci Figs. 3 and 4 as embcdied, in entrainer .frequenti emeritus of the "y resonator type having mixer-multiplier arr'a. rigernentsr and adapted f or automaticfrequency controh.

animatie vieyv illustrating a variaraiiis' bf Fig. 15., ,empmying different cav-ity ileso "Qrarrangements: ,A[Flali'LSlats'ctlo, ,aionelinelV-l 0f Eg. 6;., "Fig 8 isa diagrammatic illustration of an automatic frequency Lcontrol embodying t the, systems Dirigir ai v '1 11 a diagrammaticfview 4cian emoihe'invention similar to that of Figi'i'rfe ingspcial electron vbeam control arrangements.

L According oltthelone phase of the invention, ivision `of 1 a relatively high 'source frequency Vto a desired lowerf` fifiequericyv is obtained by ccrre ted,.,fr:equency I.mixing and feedbackV arrangements to be hereinafter described .in detail. v,l?,eferrlng. ncyv, to Fi'gal, alternating `v` voltage energy-.from any suitable `ultrahgh frequency f' v source is introduced-.by lines` lil. and l2 intothe novel automatic frequency'control arrangements mjiXer devices I3 and 14. -The. cutput.of mixer I3:is' introduced by line I5 into mixer Ill, and thelcutput o fmixer [4 is. fed back to .mixen-I3 bylne l.

Q Miners I lY and llleach may, comprise `any suitable `device capable of associating two alternating voltages andsdelivering an output, containing sum and difference frequencies." I

Assume f orpurposes of.,explanation, that the i1 hign input rquency. be designated as having .an

arbitraryyalue `of ten, representing, for example, an absolute frequency of 3000 megacycles per second,4 and itis desired to'obtain, for some purpose, a lower output frequency of one-tenth that value,

f or of .the VaIueone in ourarbtraryjscale. Hereinaft'er,` whenever the frequency valueten is Ainexition'ed', such will b 'e' understood to represent a frequ'ericiy" inthe neighborhood of 3 1 09 Amegacycles per"'secozid," and smaller' frequency values vvi'llfbe I tfbnj line syolijage having@ frequency o f iiii'ieT t'SIltlist V e value ofthe input frequency, or of the isregarding .other t f equencies, nina at@ Sum frequency? oft-rame put" df mirar is 'in iirfe l5 'win contain a side-band difference frequency of value one, which may be extracted for use on line I1 as shown.

The comparison frequency: on lead I 6 is `obtained by mixing in mixer I4 the input voltage having a frequency value of ten and the output of mixer I'3 containing .the side-band frequency of value one. This plovides that, disregarcling other frequencies, the output of mixer I4 will contain a side-band difference frequency of value nine, which is fed back into mixer I3 las illustrated.

The above explains one of the basic principles of .this phase of the invention. By utilizing proper lters for eliminating undesired side-bands and other frequencies and realizing the below-mentioned conditions, accurate frequency division may be obtained.

The above selected frequency values, of course, satisfy the conditions required to maintain an `integral l to 1 ratio in frequency, It might ap pear, however, that the apparatus may just as likely become stabilizedgto maintain any nonintegral frequency division ratio which is within the range of the filters used in the system. For example, 4should the output of mixer I3 contain a frequency of value 1.1 instead of one, the output of mixer I4 will contain a frequency of value 8.9 instead of nine, and the mixing of the input frequency ten and comparison frequency 8.9 would tend `to maintain stabilization With the output on lead II having a difference frequency of value 1.1. The frequency ratio 1G to 1.1 would .then be non-integral and undesired.

This undesirable |operation is, however, prevented by the non-linear characteristics of mixers I3 and I 4, the outputs of which contain harmonies of the input frequencies, as Well as the above-mentioned sum and difference frequencies and their harmonics. Should one of these harmonies of the input frequencies approximately coincide With a harmonic of the sum or difference side-band frequency. it Will tend to pull the mixer into step With the harmonic frequency in the same Way that an oscillator is pulled into step with a coercing frequency, so that the mixer output effectively contains only such side-bands as are related to the input frequencies by simple fracetional relationships. Such a relation is herein termed a rational relation, which term also includes an intergral-multiple relation.l

Fig. 2 illustrates this phase of the invention as embodied in an automatic frequency control system for controlling the input frequency source. Input .frequency source I8 delivers a voltage of frequency value ten to mixers I3 and I4 which are the same as in Fig. l. As indicated, a voltage having a frequency value nine is also fed into mixer I3. The output of mixer I3 therefore conltains fundamental frequencies of values nine and ten, as Well as rationally related sum and difference frequency side-bands of frequency values vone and nineteen.

The output of mixer I3 is introduced into a suitable filter Iwhich is designed to pass only the components having the frequency value one to amplifier 2| and reject .the other frequencies. The output of amplifier 2I is introduced into mixer I4 where it is mixed with the original input frequency, and the output of mixer I4 contains fundamental frequencies one and ten, as Well as rationally related sum and difference frequencies nine and eleven. A lter 22 filters out the components of all frequencies, except the difference frequency of value nine, from the output of mixer I4, and the latter 'frequency is amplified at 23 for introduction into mixer I3. The system is thereby stabilized, voltages of lower frequencies of integral values one and nine being available for any desired purpose at amplifiers 2l and 23, respectively.

Assume, as exemplary of a use of the invention, that it is desired to utilize the lower frequency voltage available at amplier 2I for automatically maintaining the input sour-ce frequency at a desired level. To this end, we extract a voltvage of frequency Value one from amplifier 2l,

,1 further amplify it at 24 and feed it into the dis- -criminator indicated at 25. This discrminator may be of any suitable type which is sensitive to changes in frequency of the voltage from am yplier 2 I, and which delivers a unidirectional output polarized according to the direction of departure of that frequency from the frequency Value one.

The output of discriminator 25 is introduced into a frequency control device indicated at 26. This device 2li is cooperatively connected to vary the frequency of source I8, either mechanically or electrically, as indicated by the dotted line. Usually control device 26 is made integral with or a part ofthe source I8.

Both filters I9 and 22 are, for this embodiment of the invention, designed to pass frequencies within anormal control range including the above-mentioned frequency values, for reasons which will appear in further description of the operation.

In operation, were source I3 and the mixer components perfectly noise-free, there probably would be no output from either mixer and the apparatus would never automatically start into operation. However, this condition can never be realized, and the system always contains inherent disturbances which enable its operation to build up, since the system is a feed-back system and has sufficient gain to make it unstable. For example, such disturbances may be due .to irregularities in the source voltage, thermal agitations in electronic discharge tubes, or the like. These disturbances are magnified by the regenerative circuit through filter 22 and amplifier 23 until a condition exists when the output of mixer I3 contains :a frequency value of approximately one, as determined by the filters, or the output of mixer I4 contains a frequency value of approximately nino.

As the device approaches full oscillation, harmonics of the input frequencies appear in the output of mixer ifi and the output 0f the device locks into step with one of these harmonies as explained.

Thus, the system is started in operation simply by connecting source I8 to energize the mixers. An initial unstable condition prevails until the required frequency values appear in the mixer outputs, and then the system becomes a stable regenerative system producing the required integral frequency division.

The discriminator and frequency control circuits do not become effective until a voltage of the desired frequency is obtained from amplifier 2l; that is, until the regenerative -control system becomes substantially stable. Then, once sta.- bility of the control circuit is attained, any depart-ure of source I8 from its desired frequency Y value ten will result in discrminator 25 exercising amplifier-2l will now have afrequency valuevof only nine-.tenths itsformer value one. The'freq-iiencyv sensitive discriminator is unbalanced and produces' the necessaryy control lsignal for actuating device 26 to retune-source I8, and restore it to the desired frequency ten. As--soon asthe desired source frequency has been restored, thev controleaction obviously ceases.

United States Letters Patent No. 2,294,942 i1- lustrates frequency discriminator and automatic frequency control arrangements with-Which the invention may be employed. Thus, discriminator 25l mayv include av source ofV referencel frequency with which the output'of amplifier 2l is oompared,A and the frequency ycontrol device responsive to the output of diseriminator 25 may comprise a control electrode a-ssociated with vthe source, and/or motor-driven vtuning mechanism such asillustrated in said patent.

It -isto be further understood, moreover, that theI invention is not limited `to automatic frequency control, but is of broader scope and use as indicated above and in the appended claims.

Figs. 3 and 4 illustrate a further embodiment of the invention, Fig; 3 illustrating the principle thereof and Fig. 4 illustrating its use in an automatic frequency control similar to Fig. 2.

Referring to Fig. 3, the source frequencycf valueten is mixedvvith the frequency of value nine in mixer I3 which is the same as in Figure 1. The outputof mixer I3 contains a difference side-band frequency of value one that isf'fed into a frequency multiplier 21 which may beof any suitable type such as that Vdisclosed in United States Letters Patent to `Hansen et al. No. 2;281','935. For use of this'phase of the invention with lower frequencies, `any conventional frequency multiplier may be employed.

Frequency multiplier 21 is ofsuch design that its output contains the harmonic frequency of value nine lwhich is fed :back to mixer I3, as in Fig. 1,'for completing the regenerative circuit.

Referring to Fig. 4, the output of mixer i3 containing fundamental frequencies of value nine and ten, and 'sum and diiferencefrequencies of value one and nineteen, 'is fed into lter I9 as in Fig.`2. The outputof lter I9, which passes onlyfrequencies within a normal control range near the frequency value one, is amplified in amplier 2I and fed into multiplier'21.

The output of multiplier 21 contains the harmonic frequency of value nine, and several other harmonics of the introduced frequency Vof value one. These harmonics are eliminated by filter 22 which passes only frequencies within a normal control range near frequency value nine. The output of lter 22 is amplified at 23 and fed Iback into mixer I3 similarly to Fig. 2. Also, as in Fig. 2, this phase of the invention is illustrated as employed in anautomatic frequency control system.

Aside from the fact that the` system of Figure 4 employs a multiplier instead of mixer I4 of Figure 2, its operation and uses are essentially the same as above described in connection with Figure v2 except that it may be necessary to employ some external arrangement, such as shock excitation, for starting the system of 'Figure 4 intol operation.

As indicated in Figures 1 and3, `and in the following embodimentafrequencies of value nine or eleven, as desired, may be mixed with thefrequency of value ten to obtain the required frequency of value one.

' Fig. 5 illustrates an embodiment oi'- the inven- 6 tioniadaptin'giprinciplesof Figs; Sand 4 to control of ultra-high frequencies in the order of 3x108 to 3f 109 cycles per second, or'higher. Here the frequency division system comprises a pair of suitably interconnected cavity resonator devices 28 and 23, one'of which is a mixer and the other a mixer-multiplier device, which facilitates automatic starting of operation of the system. I

rOne device 28 is a mixer and comprises apair of hollow metal-Walled cylindrical resonator chambers 3| and 32 connected to a third hollowmetal-walled cylindrical resonator chamber 33 as by cylindrical drift tube 34. A cathode 35, heated by filament 36 energized from battery 31, is designed `to provide a beam of electrons to be projected axially through the cylindrical resonators and drift tube. The driving voltage for the electron bearn4 is 'provided by a large battery 38 in series with filament battery 31. A smoothing or accelerator grid 39 is provided in the path of electron` beam.

Resonatc-r chambers 3l and 32 are separated by a common Wall 4U having a central grid area 4I aligned with corresponding grid areas 42 on a reentrant portion 44 of resonator chamber3i and. grid area 43 on the end of tube 34 projecting Within chamber 3.2. The .essential feature of this arrangement, which is an important part of the invention, is that the electron beam is substantially simultaneously subjected to velocity modulation at two different frequencies. The exact nature or construction of the resonators or the like producing the adjacent field portions acting onthe beam is not material. The other end of tube 34 projects Within chamber 33, terminating in a central grid area 45.

`A grid. area 41 in the further end Wall of chamber 33 is provided for permitting the electron beam to pass `irl-to a hollow cup-shaped collector electrode v48 comprising a series of stepped cylindrical sections decreasing in diameter remote from grid 4l'. This shape of electrode 48 is advantageous for preventing` return of secondary emission into; chamber 33,.and for good heat dissipation of the received beam energy.

' The resonator Walls electrode 48 and a closure 49 for the cathode comprise an evacuated envelope. Collector electrode 48 may be integral with the rwallsof resonator 33, or may be a separate element sealed thereto.

The other cavity resonator device 29 is a mixermultiplier and comprises a pair ofholloiv cylindrical metal-walled resonator chambers 5l and 52 separated by a common wall 53 apertured for mounting a drift tube 54 aligned with grid areas 55 and 56 on the opposite chamber walls. Grids 51 and 5E, respectively, are provided on the drift tube ends opposite grids 5E and 56. A stepped cylindrical collector electrode 5B, which may be integral with the walls of resonator 5l as illustrated, and which is preferably similar to electrode 48, is axially positioned to receive the electron beam from a suitable cathode surfaceil.

Cathode 6I is heated by lilainent t2 energized from battery 63 and iscarried by a cylindrical tube 64 having an annular outer flange 65. Battery 63 provides the driving voltage for cathode 6I. Tube t4 projects through a cylindrical resonator chamber 6l formed by extensions of the other chamber walls andan annular end Wall 58.,.parallel to ange 45. Cathode El is disposed well within chamber Sl, being insulated therefrom by a Vacuum tight insulating closure indicated at 49. lesonator @l is not vacuum tight. Flange'tt and wall' 68 are coextensive, vthereby providing a capacitative high frequency by-pass coupling between cathode 6| and resonator El. Alternatively this capacitative connection may be provided between tube 54 and a concentric in- Ward extension 68 of Wall 68 employed with ange `t as illustrated, or with ange 65 omitted,

or in some equivalent manner. Physically, tube 64 and cathode 6| are supported by closure 69 which is sealed to tube 64 and resonator 52 as indicated. This arrangement also provides for convenient extraction of energy from chamber El, if desired, without disturbing the evacuated condition of velocity modulation resonators 5l and 52.

Device 28 corresponds to mixer I3 of Fig. 3, while device 29 corresponds substantially to multiplier 2l' of Fig. 3.

Ultra high frequency energy having a frequency value ten is introduced from source through a suitable concentric line or wave guide 1i into concentric line l2 by which chambers 32 and 52 are excited. Chambers 3| and 5|, which are designed to resonate at frequency value` eleven are inter-connected by coaxial line '13. Finally, chamber 33 is connected to chamber 61 as by a coaxial line 'I4 having a convenient output terminal 15. A suitable amplifier '10, preferably of the velocity modulation type, is employed inline 14.

Operation.

Assuming both resonators 3i 'and 32 to be excited at their respective resonant frequencies eleven (or nine) and ten, the Velectrons in the beam passing therethroughl are subjected to successive, adjacent substantially simultaneous velocity modulation by the resonator fields. The theory of velocity modulation of an electron beam by an oscillatory eld is explained in Varian Patent No. 2,242,275. The resultant electron bunching which takes place along tube 34 is characteristic therefore of both resonator frequencies so that the amplitude of the bunches varies in accordance with the beat frequency between the two modulating frequencies. Resonator 33 is of such design as to be excited by the beam at a W frequency corresponding to that beat frequency, and to be unaffected lby the other frequencies present. In this case, the resonant frequency of resonator 33 is of frequency value one.

Energy is extracted from the hunched electron beam by the oscillatory eld of resonator 33 (for the general theory of such energy extraction see said Varian Patent No. 2,242,275) thus exciting resonator 33 at its resonant frequency of value one. Excitation of resonator 33 at frequency value one is made possible by the inherent debunching action which takes place in an electrongrouped beam and which is usually considered objectionable in cavity resonator devices. During travel of the electron-grouped beam along the drift passage, debunching of the electrons radially of the beam occurs due, for example, to mutual repulsion of the many negatively charged electrons in the groups. As a result of this debunchng, considerable electrons from the debunched groups are collected by the drift passage walls, on which opposite charges are induced, so that the current densities of the electron groups are reduced. The electrons between the bunches, being of lower density, are not so collected.

This mixer action, which is similar to rectifier detector action, produces an available low frequency component of value one in the beam entering resonator 33, which low frequency would f dicated. The resultant eldwithin chamber 52 produces velocity modulation at frequency value ten of the already density modulated beam, and the result is that while passing along drift tube 54, the beam possesses electron grouping which` is characteristic of both frequencies of value ten and one.

Therefore, the beam current has a beat, or sidebandy frequency of value eleven (or nine) formed by these respective frequencies, and resonator 5l, which is designed to resonate l at that frequency value eleven, (or nine), is excited thereby.

Device 29 functions similarly to multiplier 21 in Figs. 3 and 4, and in addition functions as a mixer. It is not necessaryto rely upon debunching for the mixingaction in the operation of device 2-8 because the thereindescribedmanner of launching is essentiallyla mixing or 'modulating action which renders thevbeat frequency of value eleven (ornine) available.

Resonator `5l of device 29 thus provides a source for exciting resonator 3i at the'required frequency value eleven (or nine).

If desired device 29 may be simply a frequency multiplier, by eliminating resonator 52 or by disconnecting line'lZ therefrom. Frequency value eleven, which is a harmonic of frequency value one, can be excited. in resonator Ei according to known hollow resonator multiplier operation.

Both mixing and multiplication are desirable to provide improved operation of the device 29. In ordinary mixer action, the mixer output is very weakin higher harmonics, especially above the third and fourth. Special means, therefore, must be provided to obtain tenth and eleventh harmonics as are required for the above operation. This production of the higher harmonics has been provided bythe special design of device 29, so that device 29 efficiently functions as both a mixer and a generator ofthe required relatively high harmonics. This novel construction and design of the device.29 is an important part of the invention.

Once the system of Figure 5 is set in operation, as through beam irregularities and the thermal or like disturbances above described, the system stabilizes itself, so that a reliable low frequency output may be continuouslyextracted as by concentric line 15. lThis output may be employed for any suitable purpose, such as for automatically regulating the input ,frequency source I8 as in Fig. 4 and as will be explained with regard to Fig. 8. Y I

It will be observed that in the preferred embodiment of the invention the mixers operate with rationally relatedfrequencies. This is preselected so that the frequency multiplication effects produced in substantially all cavity resonator devices helps the system to lock in at the desired operating frequencies.

If the input source coupled through transmission line to lin-e li. is a crystal-stabilized oscillator of the usual'ilovv power type, device 2S can then be used asa stabilized high power source for` any of the frequency valuesv one,. ten and eleven k(or nine) to be extracted by suitabletransmission lines, the wholeA system acting asl a stabilized self-oscillator.

Inv Figs. 6 and is illustrated a single duplex cavity resonator device liwh-ich has a central axis X-X A cathode Tl projects an electron beam through cylindrical resonator-chambers l and 'tgwhich are separated by a common wall 8l formed with an aperturedfgrid section 82. A smoother or accelerator griddis provided in the wall of resonator 't3 4near cathode l?.

A hollow vreentrant pole 85 extends from grid 84 into resonator 'i8 and is formed at its-free endk with a grid 83 near grid 32. Similarly, a hollow drift tube 8l extends from adjacentgrid 82 through resonator 'It and common wall 0| into the interior of a third resonator chamber 02', terminating in a grid '93.adjacent a cooperating Igrid B in the resonator far wall. A grid S3 is formed in the end of tube 8l adjacent grid 8i?. A collector electrode 95 is mounted beyond grid gft; Grids til, 86, 82, 83,' 93 and 94, and collector 94 are aligned on the axis of the electron beam from cathode 71.

At the other side of axis X-X, the resonator construction is substantially reversed. A cathode 93 projects an electron beam through resonator chambers 9T, 98 and 00j, parallel to the beam from cathode ll, but in the opposite direction.

A smoother or accelerator grid l0! in the Wall of resonator '9i near cathode St is aligned with a grid |02 on the end of a hollow pole |03 extending into resonator Sl' from 'that Wall. A grid |03 is formed in wall 9| opposite grid |02. A drifttube |05 extends from adjacent grid |03 through wall 8| into resonator 99, terminating in a grid |06 adjacent an associated' grid |01 inthe resonator Wall. A grid-wais formed on the drift tube end near grid |03. A stepped collector electrode |03 is'secured to the .resonatorz The opposite ends of drift tube beyond grid lill'. |05 are in effect reentrant polesvvithin the respective resonatorsSS and 93. `The structure of each resonator i3, ligand l0, 38 is novel in that the spaced grid bearing jpoles extendfro'm opposite end Walls. Grids |01, |02, |03, |013, |06 and |131 are along the axis of the electron beam from cathodeg.

Coaxial lines m9 and ||0 are Lprovided respectively for'introducing ultra high frequency energy into resonator 'l0 and extracting ultra high frequcncy .energy from resonator 0l. Cathodes 'il and 93`are suitably energized similarly toFig. 5, andare located ininsul'ating closures. and l2 which', together withcollector electrodes 95 and |08, maintain the interior of the whole cavity resonator device vacuum tight.

As illustrated in Fig. '7, resonator chambers 'i8 and 39 are open to each other so that they contain a substantially common oscillating. electromagnetic field.v Chambers 19 and 98 are similarly open to each other, as are chambers 02 and 30.

In operation, the electron beam fromcathode T7 is'successively velocity modulated at the indihunched electron stream, similarly to the operation of Fig. 5. The electron beam from cathode 96' is Asuccessively velocity modulated at' frequencies of value one 'and'y tem 'andi excites oscilla-tion of resonator 00 at the diderenee Vfreqf-uencyva-lue nine. The device of Fig. 6 is therefore similariin operation to that of Fig.. 5 except Vthat in Fig. 6 the resonator fields are substantially the same, and different relative frequencies are indicated. The resonator structure shown in Figs.. Gand 7 is important part of the invention.

The resonator association with the beam from cathode 'il' is essential the same as in device 23, so that the upper portion of device 'i6 functions as a mixer for producing the required low frequency one. The lower portion of device T6 isa mixer, yreversed in direction but similar inA operation to the upper portion. Instead of employing common resonators as illustrated thev upper and lower portions of device 76 could bel made separate cavity resonator devices similar to device 2'8 of Figure 5, with corresponding resonator chair-bers connected by coaxial lines similarly to -Figure 5.

Fig. 3 illustrates diagrammatically a manner in which the systems-of Figs. 5 or 6 may be-used for automaticallycontrolling the frequency of an altra high*frequencysource The high frequency output of sourcel is fed into system i8, which may comprise either of the systems of Figs. 5 or 6, andthe output lower frequency from system H8 is fed into discriminator U0. A tap 52| is provided for any desired utilization ofthe lower frequency output of the system.

Discriminator itsv is preferably the same as discriininator 25 in Fig. 4, and delivers a control signal sensed to actuate control device |22 at Aa desired value. This control, as above explained, may be accomplished by the arrangements disclosed in said Letters Patent No. 2,294,942.

Fig. 9 illustrates further application of principles of the invention to ultra-high frequency multiplier apparatus wherein relatively stabilized ultra-high frequency outputs are desired. In the specific embodiment selected for explanation of this phase of thel invention, it is desiredto producefrom a crystalfstabilized 300 megacycle .per second source |23 two ultra-high frequency outputs of 3000 and 3300 megacycles per second separated by a maintained constant frequency difference of 300 megaoycles per second.

Energy from source |23 is fed by coaxial line |24, into a frequency mixer device |25 ofthe cavity resonator type. Device |25 embodies a cathode |23 for projecting an electron beam through spaced resonators |2'l, |28 and |20. Resonatorit''v is excited to. resonance by 300 megacycle energy from source |23, and'its oscillatory electromagnetic field initiates corresponding grouping in the electron beam.

Resonator |23 is designed to be resonant .at the higher harmonic frequency of 3000 megacycles and produces further velocity modulation of the beam at that frequency when suitablyv excited. The required frequency of 3300 megacycles is thereby made availableat resonator |29, -device |25 functioning as a mixer similarly to device ,28 above explained.

A second cavity resonator device |3| vis provided for completing a stabilizedsystemfor producing energy at the required'frequencies.. A beam of electrons is passed` from cathode I 32 through successive apertured resonators, |33, |34, |35 and |36.

Resonato'r |33i's excited .at 3.00 megacyclesby energy on line |31 from sourcek |23, and causes velocity modulation of the .electron beam .at that frequency. 'Resonators |34 and |35 are designed 1 1 to resonate at 3300 and 3000 megacycles, respectively. Resonator |34 is excited at its frequency by energy introduced on line |42 from resonator |29. Resonators |33 and |34 thus produce characteristic velocity modulation leading to electron grouping in the beam from; cathode |32, and energy at the beat frequency 3000 megacycles is extracted from the beam at resonator |35. This operation is similar to that of device 28. Resonator |35 serves as a source of 3000 megacycle energy for exciting resonator |28 through line |4|. Resonator |36 is designed to resonate at 3300 megacycles and extracts energy from the grouped beam at that frequency. Output lines |38 and |39 provide the required spaced high frequencies for desired utilization. By this arrangement, the system is maintained relatively stable in operation .similarly to that of Figure 5. If desired resonators |28 and |35 could comprise a common chamber, similarly to the structure of Figure 6, and resona tors |29 and |34 could likewise comprise a common chamber. Resonator |36, moreover, serves as a buffer resonator for the 3300 megacycle output, being coupled to the device only by the electron beam, although if desired the 3300 megacycle energy is available at resonators |29 or |34 as illustrated.

Figure l illustrates a further embodiment of the invention generally similar to that of Figure 6 but including certain electron beam control features.

A cylindrical resonator body |43 is separated by Walls |44 and |45 into three spaced resonator chambers |46, |41 and |48 designed to contain alternating electromagnetic fields having reso- 1 nant frequencies of value nine, ten and one respectively.

A suitably energized cathode |49 is arranged to project an electron beam, collimated by electrode |I, through the resonators. The beam passes through a smoothing grid |52, a reentrant conical pole |53 within resonator |46, aperture |54 in Wall |44, an oppositely facing reentrant conical pole |55 in resonator |41, a cylindrical tube |56 in resonator |48 forming with pole |55 a drift passage, and a relatively small aperture |51 in the center of a ldisc |55 otherwise closing the end of tube |56. A grid |59 and collector electrode |6| are arranged in the path of the beam beyond resonator |48.

The electron beam is a relatively small diameter concentrated stream of electrons for most efficient interaction with the high frequency fields within resonators |46 and |41. As in Figure 6 the beam is velocity-modulated by the fields of resonators |46 and 41 to `produce electron concentrations along the beam characteristic of both frequency values nine and ten, so that the beam contains electron concentrations corresponding to the difference frequency Value one for excitation of resonator |48.

As the electron concentrations pass along the drift passage |55, |56 radial debunching takes place due to space charge effects arising from mutual repulsion of the electron charges. Due to this debunching, the beam has fewer electrons near its axis in the regions of electron concentra- ,tions than in the regions between those concentrations.

lcentral zone of the beam. These centrally located electrons so passed are disposed in periodic electron density concentrations whichV are inversely related to the original concentrations, but

ywherein the outer debunched electrons in the beam are intercepted, reference is made to the copending application of Varian and Relson Serial No. 490,962, filed June 16, 1943, now Patent No. 2,414,843, dated January 28, 194'?.

A second cathode |62 projects an electron beam,

jcollimated by electrode |63, through the resonators parallel and opposite to the beam from cathode |49. This second electron beam passes through a smoothing or accelerator grid |64, a cylindrical reentrant pole |65 extending into resonator |48, a grid |66 on the end of pole |65, a grid |61 in wall |45, a conical reentrant pole |68 extending into resonator |41 from Wall |44, and an opposite conical reentrant pole |69 extending into resonator |46. A grid |1| and a collector electrode |12 are also arranged in the path of the electron beam.

The electron beam from cathode |62 is also a relatively small diameter concentrated electron stream. Poles |68, 69 serve as a drift passage, and pole |69 has a relatively small exit aperture at |13 whereby pole |69 functions similarly to disc |58 in intercepting the debunched electrons in the outer annulus of the electron concentrations passing therethrough,

The device of Figure l0 operates similarly to that of Figure 6. The high frequency of value ten, to be divided, is introduced into resonator |41 by coaxial line |14, and the low frequency output of frequency value one is extracted from resonator |48 by coaxial line |15. As above explained resonator |48 is excited at frequency value one by the beam from cathode |49. The electrons in the beam from cathode |62 are velocity grouped by the fields of frequencies of value one and ten, and then the difference frequency Value nine excites resonator |46 to provide a source of frequency value nine for the initial mixing operation.

As many changes could be made in the above construction and many apparently Widely different embodiments of this invention could be made Without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. Apparatus for automatically controlling the frequency of an ultra-high-frequency oscillator, comprising means coupled to said oscillator for producing a signal at a relatively low frequency equal to a predetermined fraction of the ultrahigh frequency of said oscillator, and means coupled to said signal-producing means and responsive to variations of said low signal frequency from a predetermined value for adjusting the tuning of said ultra-high-frequency oscillator to suppress said variations from said predetermined value, said means for producing said low frequency signal comprising a rst mixer and a second mixer both coupled to said oscillator to receive. ultra high frequency energy therefrom, frequency selective means responsive to energy of a further frequency different from said ultra high frequency by an. amount equal tofsaidrelatively low frequency andcoupled. .to saidiirst mixer to receive therefrom energy at said further frequency and also coupled to said second mixer for delivering thereto energyat said 'further frequency, and additional. frequency selective means responsive to said .relatively low frequency coupled to said second mixer for .selectively receiving therefrom energy at said relatively low frequency, said additional frequency selective means being coupled to said first'miXer for delivering thereto a portion of the :energy at said. relatively low frequencyreceived from said second mixer.

2. Apparatus for automatically controlling the frequency of an ultra-high-frequency oscillator, comprising means coupled. to said oscillator for producing a. signal at a relatively low frequency equal to a predetermined fraction of the ultrahigh frequency of said oscillator, and means coupled to said signal-producing .means and responsive to variations of said low signal frequency froma predetermined value for adjusting the tuning of said ultra-high-frequency oscillator tosuppress said variations from said predetermined value, said means for producing .a signal at a relatively low frequency equal to a predetermined fraction of said ultrahigh frequency comprisinga mixer coupled to said oscill'ator to receive ultra high frequency energy1 therefrom, frequency selective means coupled to said mixer to receive therefrom energy at said relatively low frequency, frequency multiplier means coupled to said frequency selective means for.. producing an output signal at a predetermined multiple of said relatively low frequency, and means for delivering said output signal from said multiplier to said mixer whereby said frequency multiplier output energy is mixed with said ultra high frequency energy to produce mixer output energy at saidrelatively low frequency.

3. Apparatus for automatically controlling the frequency of a high .frequency source comprising means for mixing energy from said source with energyhaving a rationally related frequency for obtaininga lower frequency output, means controlled by sa-id lower frequency output for providing-said' energyof said rationally related frequency, means feeding back said rationally related frequency energy into said mixing means, and means coupled to said lower frequency output and` responsive to frequency changes thereof for controlling the frequency of .said source.

4. Electronicapparatus comprising means defining a pair of adjacent electromagnetic fields oscillating at different frequencies, means for projecting an electron beam through said fields so that the electrons in said beam are subjected to velocity modulation by the respective fields, a third.' electromagnetic eld coupled with said modulated beam forextracting energy therefrom having a `frequency representing the difference between said frequencies, and Vmeans for obtainingenergy from said third eld. y

55.' Electronic apparatus comprising an associn ated pair of resonant chambers containing electromagnetic elds oscillating at different frequencies, means for projecting an electron beam through said fields so that said -beam is subjected to successive velocity modulation by said fields, drift passage means wherein the electrons in 'aces-epee said beam. becomegroupied as afresult' of said velocity modulation, a third resonant chamber adapted.. to receive said velocity-grouped beam and extract therefrom energy having a frequency yequal .to the. difieren-ce i of .said frequencies, land means. for:obitair'iing.` energy fromfsai'd` third reso nant chamber.

`6; The apparatusdefined in claim v5, wherein one of .said'elds is` excited by 'an' availablesource and...energ.ization. of. thel other ofsaid .fields is controlled by tneoutput of saidl third vresonant chamber...

'7...'lhe.Y apparatus definedyin claim 5:, Whe-rein means. arefprovidedvfor :excluding .electronsffrem thethird. chamber `in proportion to the degree of grouping insaidrbeam.

8.' Thefapparatus donned, claim l5 including a cavity. resonator frequency multiplier device havingan input resonant chamber coupled to the Aoutput of .said third resonator, `and mean-s coupling the outputrresonator of said frequency .multiplier device' to. excite one lof said. fields.l

9., The` apparatus definedinclaim 5, including a cavity resonator: device having three resonant chambers coupled respectivelyito said first-named chambers.

10'. Electronicapparatus comprising av cavity resonator device embodyingI twocavityfresonators adapted to contain oscillating electromagnetic fieldsAA having different frequencies, means .for projecting an electron. beamthrough said fields, lvsaid fields .producing electron grouping in said beam, a third resonator infsaid device coupled to :said electron grouped beam. inA energy interchanging relation therewith, a second cavity resonator,` device hailing afirs-t yresonator adapted to be coupled to the outputv Of they thirdresonator of'sai-d first devi-ce, means for projecting,l a second electron beamrthrough saidnrst `resonator of saidsecond device,` a second resonator in said second device coupledtosaidsecOnd electron beam in energy interchanging relation therewith, and means coupling';r said'l second resonatorv of said second device to one of said two resonators. `ofsaid irst devi-ce.

11.. The.apparatus .deiinedri-n'iclaim 10, wherein saidrcoupledi resonatorsghave common electromag.J neticfields..y

12. Electronic apparatusrof theicavi-ty-resonator type comprisingfmeans .defining `three-,spaced .resonator-chambers, meansfor-:projecting a pair of spaced electron: beamsA inA opposite. directions through; .said :.chambersr; means for 'couplingA each .ference between said field'ffrequencies, and means responsive to said bearnfproviding an electromagnetic eldfzoscillating; at .said difference -frequency.

14; Ultra high frequency'apparatuswcomprising means defining a pair of associated resonator chambers having different resonant frequencies, means for passing an electron beam through said chambers, means dening a third resonator chainber into which said beam is projected, said third chamber having a resonant frequency different from either of said other two chambers, and means providing a drift passage through which the beam passes between said pair of chambers and said third chamber.

15. Ultra high frequency apparatus comprising means defining a plurality of electromagnetic eld regions having substantially harmonically related resonant frequencies, means passing an electron beam successively through said eld regions for energy exchanging interaction therewith, means defining a plurality of further electromagnetic field regions having said substantially harmonically related frequencies, means passing a second electron beam successively through said further field regions for energy exchanging interaction therewith, and means for coupling one of said eld regions to one of said further field regions having the same resonant frequency.

16. Ultra high frequency apparatus comprising means defining a plurality of cavity resonator chambers having different resonant frequencies, means projecting an electron beam through said chambers in energy exchanging relation with the fields contained by said chambers, means defining a plurality of further cavity resonator chambers having said different resonant frequencies, means passing a second electron beam through said further resonator chambers in energy exchanging relation with the fields contained by said chambers, and means for coupling the field within one of said first named resonator chambers to the eld within that one of said further resonator chambers having the same resonant frequency.` 17. Ultra high frequency apparatus comprising means producing a beam of electrons, mixer means providing a pair of resonant circuits having different frequencies arranged to substantially simultaneously interact withsaid beam for initiating electron grouping corresponding to saidffrequencies along the beam,and a third resonant circuit coupled to said grouped electron beam for extracting energy therefrom, said third circuit having a frequency which is a function of both said different frequencies. 1

18. The apparatus defined in claim 17, wherein each of said resonant circuits comprises a hollow resonator coupled to the beam through apertured walls, and wherein the apertures of the first two resonators are closely disposed.

19. The apparatus defined in claim'17 wherein said different frequencies 4are bothharmonics of thev frequency of said third circuit.l

`20. Electronic apparatus comprising means for producing an electronstream, electrode means positioned along the path of said stream and dening three gaps traversed'successively by said Stream, means defining alfield-free drift space between the second and third of saidgaps, means producing a rst oscillating electric neld of a first frequencyat the first of said gaps, means producing a second oscillatingelectric field of a diiferent frequency at said second gap, and output circuit means coupled to said third-gap-dening quency, means for velocity modulating said stream at a second frequency, means defining a fieldfree drift space surrounding the path of said stream beyond said modulating means, and means beyond said drift space for inductively extracting energy from said stream of a frequency different from said first two frequencies.

22. Ultra high frequency apparatus comprising means providing an electron beam, means for imparting electron density modulation of two different frequencies to said beam, means providing a resonant circuit having a resonant frequency equal to the difference of said frequencies, means providing interaction between said modulated beam and said circuit, means providing a second electron beam, means actuated by said resonant circuit for imparting electron density modulation to said second beam of the frequency of said circuit, means for imparting density modulation to said second electron beam of a frequency equal to one of said first-named frequencies, means extracting energy from said second beam at the other of said first-named frequencies, and means utilizing said extracted energy for causing modulation of said first beam at said other frequency.

23. The apparatus dened in claim 22, wherein means are provided for excluding a part of said first beam from said resonant circuit in proportion to the combined amplitude of said two density modulations.

24. Electron discharge apparatus adapted to multiplication of ultra-high frequencies comprising means including a cathode for producing a stream of electrons, a grid mounted in the path of said stream adjacent said cathode, a resonator coupled between said grid and said cathode and tuned to a fundamental frequency, a `second grid positioned along said stream path opposite said first electrode, and a second resonator tuned to a harmonic of said fundamental frequency and coupled to said pair of grids.

25. Apparatus as in claim 24, comprising a further cavity resonator positioned along said stream path for interaction with said stream at a position spaced from said pair of grids, said lastnained resonator being tuned to a different harmonic of said fundamental frequency.

WILLIAM W. HANSEN. RUSSELL H. VARIAN.

REFERENCES CITED rlhe following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,450,966 Affel Apr. 10, 1923 2,039,657 Osborne May 5, 1936 2,124,191 Greiger July 19, 1938 2,159,595 Miller May 23, 1939 2,159,596 Miller May 23, 1939 2,159,597 Miller May 23, 1939 2,180,816 Miller Nov. 21, 1939 2,250,284 Wendt July 22, 1941 2,280,824 Hansen et al Apr. 28, 1942 2,281,935 Hansen May 5, 1942 2,305,883 Litton Dec. 22, 1942 2,317,140 Gibson Apr. 20, 1943 2,336,926 Crosby Dec. 14, 1943 

